Many component parts of a gas turbine engine include cooling holes for active cooling of engine sections located downstream of the turbine section. The rising combustor exit temperatures in gas turbine engines necessitate active cooling to avoid thermal failure. For example, a transition piece for a gas turbine engine typically includes an integral frame portion surrounding an opening at a downstream end where the transition piece connects to the turbine stage. An exemplary transition piece is described in U.S. Pat. No. 5,414,999.
Under the high temperature operating conditions of the gas turbine engine, fracture or cracks may occur around the cooling holes located on portions of the frame. Failure analysis has revealed that such cracks form perpendicular to the inner surface of the frame, which indicates that thermal stresses played a role in forming the cracks occurring at the cooling hole. Grain boundary oxidation and thermal fatigue are potential causes of such cracking. Cracks initiated at the cooling holes on the aft-facing end of the frame and propagated into the body of the frame. Analysis indicated that cracks in the cooling holes of the frame followed the oxidized grain boundaries. Currently there is no process to prevent crack initiation at the aft end of the cooling holes.
There is a need for local reinforcement of cooling holes in a gas turbine component. There is also a need to provide enhanced oxidation resistance around the cooling holes to reduce oxidation and cracking along grain boundaries.
Intended advantages of the disclosed systems and/or methods satisfy one or more of these needs or provide other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.